Farm tire designs for industrial service are classified as R4 service. Overall R4 service is quite severe and typically involves high loads at a large degree of roading. The vehicles to which the tires are mounted typically are exposed to large amounts of debris, hard packed soil conditions and high load service conditions.
Often times the vehicle has a back hoe bucket or a front skid loader attached to the vehicle. The tires must traverse gravel and broken concrete and hard packed dirt normally. Occasionally the work site can get rain soaked requiring good traction in wet soil conditions.
These tires are generally relatively small and typically have a nominal rim diameter of 28" (71 cm) or less. They generally have a nonskid depth at the centerline of the tire at approximately 1" (2.54 cm). A typical tire may be a 19.5LR24 tire. This tire when produced in a radial construction will have a carcass with 3 to 4 plies of synthetic cord reinforcement. The cords generally are nylon or polyester. The carcass will further include four belts of high flex polyester, nylon or aramid. Historically, these tires have been all fabric reinforced in order to provide better ride and handling.
The most relevant prior art is Japanese Publication No. 57167802, the tire of this invention travels well on both good and soft roads. Its tread pattern consists of three regions with almost the same width. At the two side regions, lugs are arranged alternately on the tire circumference to form arrowhead pattern. They are at an acute angle to the tire equator. At the central region, independent long blocks are laid across the tire equator. Each block is placed on a line extended from the longitudinal centerline of one lug located on one of the side regions. The adjacent blocks face each other and overlap for a certain range but separated by a groove along the equator.
Another prior art document, U.S. Pat. No. 4,659,976), discloses a tire for use on a military vehicle, the tire has traction elements separated by straight grooves.
Yet another prior art, (German Patent No. DE 27 51 295 A1), discloses a farm tire having elongated lugs 6 spaced from the center of the tread and in at least one embodiment, the lugs 6 are separated by square blocks 9.
There has been a continual tradeoff in attempting to increase the aggressive offroad and tractor performance of these tires while maintaining the treadwear durability and ride requirements. The invention disclosed in this patent application teaches a novel tread that is both comfortable riding, long wearing while also achieving superior offroad traction.